How about a surrealistic episode where the producers tell the characters it's over?
At the very beginning, Larry David himself would walk out and tell the characters that they're just characters in a show, that he's sick of how nasty they are or whatever he wants.
He tells them how much time they have left and splits. Then, they're on their own with the certain knowledge that their "lives" are over and why.
As long as he's gonna disown the show, why not make the finale pleasant to watch? Hell, once you've got the producer stepping in and breaking the fourth wall, you could pull in as many characters as you want without the need for clips or explanation!